The XSetInputFocus
function changes the input focus and the last-focus-change time. It has
no effect if the specified time is earlier than the current last-focus-change
time or is later than the current X server time. Otherwise, the last-focus-change
time is set to the specified time (CurrentTime is replaced by the current
X server time). XSetInputFocus causes the X server to generate FocusIn
and FocusOut events.

Depending on the focus argument, the following
occurs:

·

If focus is None, all keyboard events are discarded until a
new focus window is set, and the revert_to argument is ignored.

·

If focus
is a window, it becomes the keyboard's focus window. If a generated keyboard
event would normally be reported to this window or one of its inferiors,
the event is reported as usual. Otherwise, the event is reported relative
to the focus window.

·

If focus is PointerRoot, the focus window is dynamically
taken to be the root window of whatever screen the pointer is on at each
keyboard event. In this case, the revert_to argument is ignored.

The specified
focus window must be viewable at the time XSetInputFocus is called,
or a BadMatch error results. If the focus window later becomes not viewable,
the X server evaluates the revert_to argument to determine the new focus
window as follows:

·

If revert_to is RevertToParent, the focus reverts
to the parent (or the closest viewable ancestor), and the new revert_to
value is taken to be RevertToNone.

·

If revert_to is RevertToPointerRoot
or RevertToNone, the focus reverts to PointerRoot or None, respectively.
When the focus reverts, the X server generates FocusIn and FocusOut
events, but the last-focus-change time is not affected.

XSetInputFocus
can generate BadMatch, BadValue, and BadWindow errors.

The XGetInputFocus
function returns the focus window and the current focus state.

Some numeric value falls outside the range of values accepted by the
request. Unless a specific range is specified for an argument, the full
range defined by the argument's type is accepted. Any argument defined as
a set of alternatives can generate this error.